• Todo/a/s and ambos/as must agree in gender and number with the noun they modify or replace:
| Va a llover toda la primavera. Todos los problemas son fáciles. Todos cometemos errores. Ambos días hizo sol. Ambas fueron semanas de lluvia. |
It’s going to rain all (the whole) spring. All (of the) problems are easy. All of us (we all) make mistakes. It was sunny on both (of the) days. They were both rainy weeks. |
• ambos is never accompanied by articles:
ambas ciudades both of the cities
• A common equivalent of ambos is los dos:
Ambos conocemos Panamá y Caracas, y las dos hace calor.
Both of us know Panama and Caracas, and both of them are hot.
• Subject pronouns can be used after todos (not after ambos or los dos):
Todas ellas saben nadar. All of them know how to swim.
Note that todo/a/s and ambos/as are never followed by the preposition de.
• Todos often translates into “every” in the sense of “all the”:
| todos los días todas las clases Sé todo lo que hiciste este verano. |
every day all of the classes I know everything (that) you did this summer. |
• When stressing individuality (each), “every” translates into cada:
Conoce cada detalle del cuento. She knows every detail of the story.
Llamó a cada uno por su nombre. He called each one by their names.
“Every other” is expressed by cada dos: cada dos años, cada dos días.
Both…and is tanto…como (no gender or number). Never use ambos for both…and:
Tenemos clases tanto los lunes como los miércoles.
We have classes both on Mondays and on Wednesdays.
Practice
Translate half of the sentences into Spanish.
1. All of the South American countries voted against (contra) the resolution last week.
2. Every representative expressed her own reasons, but all of them agreed (estar de acuerdo).
3. Yesterday, however, both the Argentine and the Uruguayan changed their votes.
4. Both of them decided to defend their mutual interests against the majority.
5. This was both surprising (sorprendente) and irritating (irritante) for all representatives.
6. Something similar occurs every year. They continue to debate these problems.
(source)